PRESERVATION Tech Notes NATIONAL PARK SERVICE U.S. DEPARTMENT OF THE INTERIOR WASHINGTON , D.C. METALS NUMBER 2 Restoring Metal Roof Cornices Richard Pieper Director of Preservation Jan Hird Pokorny, Architects and Planners 32 EAST 64TH STRET New York City 32 East 64th Street is a prominent features is its oversized classically cooperative apartment building at the detailed sheet metal cornice. Close to 8' corner of Madison Avenue and Sixty­ high, it projects nearly 6' from the fourth Street in New York City's masonry facade and is 260' long. Upper East Side Historic District. Following a careful study of the Known as "The Verona" when deteriorated condition of the cornice, constructed in 1907, the building was repairs were undertaken to renew this designed in the "Neo-Venetian prominent feature of the building. Renaissance" style. The first floor of the I O-story structure is rusticated Problem limestone, while the upper floors are In 1986, the firm of Jan Hird Pokorny iron-spotted buff Roman brick, with Architects was hired by the building intermediate cornices, balustrades, and owners to inspect and evaluate the Decorative metal roof cornices window surrounds of buff matte glazed condition of the cornice and provide terra cotta intended to imitate stone. recommendations for any necessary should be repaired rather than One of the building's most prominent corrective work. The cornice was replaced wherever possible. found to be extremely deteriorated. relatively good condition. In spite of Large sections of stamped zinc recurrent leakage, the tiles were in ornament were perforated and satisfactory condition, and the trusses separating from the brake-formed showed only small areas of superficial galvanized steel that formed the lineal rusting. The galvanized steel facing of moldings of the cornice. the cornice was generally in good The unusually large size of the condition, but about 30 lineal feet cornice made it possible to inspect its (roughly 10 percent) of the steel at the interior (see figure 1). It was accessible base of the cornice had rusted where through two small hatches in the the galvanized facing entered the sloped roof covering the rear of the masonry wall. (Water leaking into the cornice trusses. The cornice itself is cornice had collected there.) In supported by steel trusses, which are in addition, large rust holes had formed turn attached to the structural steel behind nearly all the decorative lions' frame of the building (see figure 2). heads on the crown of the cornice, The top and rear slopes of the cornice where holes in the exposed and seldom trusses are covered with structural clay painted ornament allowed bird nests tiles supported by 2" steel tee purlins and moisture to accumulate. The metal set perpendicular to the trusses. The of the cornice soffit was in surprisingly Figure l. Large steel trusses cantilever out from tiles served as a base for the terne­ good condition, perhaps because water the masonry parapet to support the cornice. plated steel standing seam roofing, entering there was able to weep Metal facing of the cornice was bolted to small which had rusted through in spots on through lapped seams of the steel iron or steel ribs (as at left). Wire ties helped to the top slope. The standing seam roof facing. pull the center of the cornice tight to the bottom on the rear slope of the cornice had Other leakage was attributable to a member of the truss. Photo: Richard Pieper. been coated with asphalt but was in small sloped section at the front of the ~=~;;:;;::;::;::;::;~::;::;::;::;::;~::;::;~~~~:-_NEW PRESSURE TREATED 2"x6" AND 3/4' PLYWOOD '1 DECK WITH MODIFIED BITUMEN ROOFING • .l,-l1~~--STEEL CORNICE TRUSSES APPROXIMATELY 6' -0" O.C. ~a.-- STEEL "T" PURLINS CORNICE HEIGHT \\ ........- STRUCTURAL CLAY TILE APPROX. 8'-0" CLADDING MORTARED TO PURLINS EXISTING GALVANIZED ----~o:--~ STEEL FACING RETAINED X NEW EGG AND DART MOLDING./ EXISTING GALVANIZED STEEL ~ DENTILS RETAINED 1 NEW 6" STAMPED ZINC LEAF ~ MOLDING RIVETTED TO REPAIRED GALVANIZED STEEL BACK-UP CORNICE PROJECTION APPROX. 6' -IY' STEEL TRUSSES EMBEDDED IN PARAPET MASONRY AND CONNECTED-;:ffij;-----1K4~~t:==========~~~ TO STEEL FRAME IN ROOF SLAB EXISTING ROOF SLAB Figure 2. Cornice section shows the manner in which the cornice was supported al1d attached to the building. Drawing: Michael Devonshire. 2 NEW MODIFIED BITUMEN MEMBRANE 314' EXT. PRESSURE·TREATED PLYWOOD NEW 20 OZ. GALVANIZED STEEL ROOF EDGE AND FASCIA. ........1--- 2" x 6" PRESSURE·TREATED WOOD DECKING EXISTING ORIGINAL ROOF EDGE -------+----..... ~ 000 NEW FASCIA AND CROWN MOLDING ______ ... BOLTED AT ENDS OF SHEETS AND ~ RIVETED AT OVERLAP ABOVE LIONS' HEADS NEW 20 OZ. GALVANIZED STEEL CROWN MOLDING BOLTED TO EXISTING DETERIORATED CROWN MOLDING AND TO RIBS. NEW STAMPED ZINC LION HEADS TO ___ ... REPLACE ORIGINAL, BOLTED TO ----. GALVANIZED FACING ¥.6" THREADED ROD ARMATURE SUPPORT AT ALTERNATE RIBS TO SUPPLEMENT EXISTING BASE OF NEW CROWN MOLDING BOLTED _----~_:::r'W':.,. WIRE TIES. AT ENDS OF SHEETS AND RIVETED EXISTING I"x v.," STEEL ARMATURES ROUGHLY 6" O.C. FOLWW CONTOURS OF CORNICE FACING; USED TO WIRE CORNICE TO TRUSSES. EXISTING 3" STAMPED ZINC EGG AND ------------..~ ARMATURES ARE SPACED APPROXIMATELY DART MOLDING-THE ONLY ORIGINAL 3'·0 " ON CENTER STAMPED ORNAMENT TO REMAIN 1 V2" PIPE CLAMP EXISTING GALVANIZED STEEL FACING TO REMAIN ----------tl~ Figure 3. Detail section shows the new cornice crown molding, edge cap and roofing that corrected a construction flaw in the original fabrication. Drawing: Michael Devonshire. cornice above the crown molding (see figure 3). Perhaps due to a fabrication error, the trusses were too tall to receive the cornice facing as designed. Since the facing could not be raised further vertically without the top inside corner of the modillions touching the bottom chord of the trusses, a gap existed between the top of the sheet metal facing and the cornice roof when the facing was installed. The gap was closed by a short sloped piece of galvanized steel sheet metal that was not visible from the street. By far the most serious problem with the cornice was the deterioration of the stamped zinc ornament applied to the exterior of the galvanized steel facing. The large l2"-wide zinc modillions projected 24" from the cornice entablature and were in poor condition. The stamped zinc had fractured where integral leaf moldings Figure 4. As shown in this view, the molding applied to the modillions was extremely deteriorated. A met the scrolled sides of the more serious problem was that most of the zinc modilIions had fractured where the integral leaf moldings met the scrolled sides, allowing them to separate from the soffit. As a previous temporary modillions, allowing them to separate safety measure, holes had been cut in the soffit panels to pass supporting wire beneath the modilIions. from the soffit. As a previous Photo: Richard Pieper. temporary safety measure, holes had 3 been cut in the soffit panels to pass supporting wires beneath the modillions (see figure 4). Cracks indicative of metal fatigue were also present in the fronts and sides of the modillions. Most of the applied stamped zinc moldings were also extremely deteriorated. The cornice had been infrequently painted, and much of the ornament was thinned, perforated or broken through dissolution and embrittlement of the zinc. Lions' heads on the crown molding could easily be punctured and were tenuously attached to the galvanized steel with deteriorated soldered joints. Sections of leaf molding and egg and dart molding at the base of the cornice had fallen or been removed. The remaining molding was in poor condition (see figure 5). Solution Figure 5. Most of the egg and dart molding on the cornice had deteriorated over the years and required replacement. Photo: Richard Pieper. Inspection showed that the galvanized steel facing of the cornice was in repairable condition but that much of the applied zinc ornament was not salvageable. The trusses supporting the cornice, the steel tee pUrlins and the structural clay tile were generally in excellent condition. Budget estimates were prepared for repair-in-kind and for replacement of the cornice. The architects considered two replacement alternatives; one with new metal and one with glass-fiber reinforced plastic. Repair of the existing cornice facing was the most economical alternative. The New York City Landmarks Preservation Commission also favored repair rather than replacement. Repair of the cornice included replacement of all modillions and nearly all applied zinc moldings; installation of new galvanized steel crown molding and cornice roof edge details; placement of new roofing on the top of the cornice; insertion of new rod hangers to Figure 6. Three of the components of the metal cornice which required replacement because of serious supplement existing wire hangers deterioration are shown in this view. They are the lions' heads on the crown molding (several are supporting the face of the cornice, and missing due to failed soldered joints), modillions, and the egg and dart molding at the base of the repainting both the interior and cornice. The brake-formed galvanized steel that comprised the lineal moldings of the cornice, the soffit and dentil band were in sound condition. Photo: Richard Pieper. exterior (see figure 6). impossible to examine all portions of work on modillions and molding Work Description the front face of the cornice from replacement below the soffit, and an Visual examination of the exterior of swing stage scaffolding. For these upper level to replace roof edging, the cornice with binoculars showed reasons, a 20' long fixed tubular crown molding, and lions' heads. that significant sections of stamped scaffolding tower was erected on molding had previously separated from sidewalk bridging to facilitate Paint Removal the galvanized steel substrate and had inspection of a representative portion Existing paint was flaking and peeling.